1. Field of the Invention
This invention relates to earth boring bits, lubricated with a system which includes a hydrostatic pressure compensator to balance the internal pressure of the lubricant inside the bit with the hydrostatic pressure of a liquid drilling fluid that surrounds the bit during drilling. In this combination the specific improvement relates to the seal assembly between each cutter and bearing shaft which confines lubricant within, and excludes contaminates from, the bearing and lubrication system.
2. Description of the Prior Art
The successful application of rigid (usually metal) face seals in the harsh environment, including severe pressure fluctuations, found during the drilling of deep wells for petroleum and minerals culminated in the structures disclosed in my above identified U.S. Pat. No. 4,516,641. In this patent the preferred embodiment may be referred to as the "roll/compression" metal face seal.
There is another class of seals known as the "shear/compression" metal face seal, one example of which may be seen in U.S. Pat. No. 4,421,327, "Heavy Duty End Face Seal With Asymmetrical Cross-Section", Dec. 20, 1983. An example of an attempt to apply the shear/compression seal to earth boring bits may be seen in U.S. Pat. No. 4,466,622, Compound Dynamic Seal For Rolling Cutter Drill Bit, Aug. 21, 1984.